1. Field of the Invention
The present invention relates to graphene devices and, more specifically, to a gated graphene device.
2. Description of the Related Art
Graphene has demonstrated numerous properties that make it suitable as a material for electronics. An important property of graphene is that its conductivity depends on the density of charge carriers (either electrons or holes) in the graphene. For example, when a voltage difference is applied between the ends of a graphene ribbon then a current will flow through the ribbon. The magnitude of the current depends on the density of the charge carriers in the graphene ribbon. This density can be modified using an electrostatic gate that selectively applies an electric field to a portion of the graphene ribbon, thereby modifying the resistance of the graphene ribbon in the vicinity of the gate.
Existing graphene electronic devices typically employ an electrostatic gate that includes a dielectric material that is deposited on a graphene sheet and a metal layer that is deposited on the dielectric material. Applying a potential difference between the metal layer and the graphene ribbon establishes an electric field at the graphene ribbon, which modifies the charge density in the graphene ribbon and its conductivity.
The effectiveness of the electrostatic gate is measured by the magnitude of the potential difference that is required to produce a certain change in the conductivity of the graphene ribbon. Typically, thinner dielectric layers are preferable. However, a dielectric layer that is too thin tends to leak and undesirable current flows from the metal layer to the graphene ribbon.
Applying a dielectric material to the graphene can be difficult because many dielectric materials do not adhere well to graphene. Therefore, graphene is typically modified chemically when applying a dielectric layer thereto. However, such chemical modification can degrade the quality of the graphene. Also, it is difficult to produce sufficiently thin dielectric layers on graphene using most conventional processes. This results in a need for relatively large potential differences to be applied between the gate and the graphene ribbon to produce a suitable gating effect in active graphene electronic devices.
Therefore, there is a need for a method of applying a gate to graphene that does not require application of a dielectric layer.